[3.13] gh-101100: Fix Sphinx nitpick in unittest.mock.rst (GH-151302)

(cherry picked from commit b18168c)

Co-authored-by: Cody Maloney <cmaloney@users.noreply.github.com>

Author: miss-islington

Doc/library/unittest.mock.rst

@@ -2223,7 +2223,7 @@ return something else::
    >>> mock == 3
    True
 
-The return value of :meth:`MagicMock.__iter__` can be any iterable object and isn't
+The return value of :meth:`!__iter__` can be any iterable object and isn't
 required to be an iterator:
 
    >>> mock = MagicMock()

Doc/tools/.nitignore

@@ -35,7 +35,6 @@ Doc/library/test.rst
 Doc/library/tkinter.rst
 Doc/library/tkinter.scrolledtext.rst
 Doc/library/tkinter.ttk.rst
-Doc/library/unittest.mock.rst
 Doc/library/urllib.parse.rst
 Doc/library/urllib.request.rst
 Doc/library/wsgiref.rst